All electronics assembly manufacturing lines require some form of component placement system. The simplest component placement equipment is a steady hand and a pair of tweezers. More complex systems use automatic component placement machines, and, as in manual placement, the object is to pick up a part from a certain position and place it at a new location on a substrate. Pick-up is normally achieved either in manual or automated systems by using a vacuum chuck which is sized to suit the component. Components are presented to the pick-up position using an automatic component feeder. In all cases, two important criteria for component placement are accuracy and reliability. The ability to repetitively place the component in the desired location on the substrate. Repeatability of component placement is typically aided by the use mechanical centering jaws on the placement head. The placement head then typically moves from the pick up position to the desired location on the substrate and deposits the component on the substrate by releasing the vacuum, thus allowing the component to gently fall into the desired location. Components are typically placed, in to an adhesive or a solder paste that prevents the movement of the component during subsequent operations. Both the solder paste and the adhesive have a certain degree of tackiness which tends to hold the component in position.
Two major approaches are typically taken on automated pick and place equipment for surface mount technology. The first is to use a dedicated head for each component. This head transfers components from a feeder to the substrate or printed circuit board (PCB). A conveyer moves the boards past a line of placement heads which progressively populate the board. This type of system is typically used for very high volume, long run situations. The second approach is a single head machine which is microprocessor controlled and contains numerous interchangeable chucks which can rapidly pick parts from a variety of feeders and populate a single board at a time. This approach is more appropriate for short to medium runs with many different assemblies, since set-up time is relatively short and the machines are very flexible.
The level of "user friendliness" should be considered in any decision as to which type of component placement head to use. While some machines require technician level personnel to program and edit machine functions, others require more skilled engineering level assistance. The trade off between flexibility and cost of maintenance must be considered by the user.
In the case of single head component placement machines with multiple chucks, 100 or more vacuum chucks are on a single head. It is extremely important that each of the chucks be maintained in a pristine operating condition. If any of the chucks is misaligned or inoperative, the placement of the components will be in error or the component will be missing from the circuit board. High speed machines that have turret heads are capable of placing very high numbers (5000-8000 per hour) of small components, and the problem of vacuum chuck or vacuum nozzle clogging is a significant one. The small orifice in the vacuum chuck is easily obstructed by environmental debris or particulates. In order to ensure continued up-time and reliability of machines, the vacuum chucks must be scrupulously cleaned on a regular basis. In addition, there is no way of determining whether a vacuum nozzle is obstructed until it becomes completely inoperative, at which time defective product has already been manufactured.
It would be desirable and a significant improvement in the state of the art, if a system could be devised that could detect a clog or obstructed vacuum nozzle in a proactive manner. Such a method would reduce the cost of maintenance of the high speed component placement machines and increase the quality of the assembled electronic product.